System and methods for mitigating interferences between electrosurgical systems

ABSTRACT

Methods and system are provided to mitigate RF interferences during operation of an electrosurgical system. An electrosurgical system configured to output therapeutic RF energy may refrain from outputting RF energy in order to measure an RF interference for a group of candidate frequencies, and to select a frequency from the group of candidate frequencies for which the measured RF interference is below a threshold value, and to produce a feedback signal (a control signal) at the selected frequency to control operation of the electrosurgical system. During operation of the electrosurgical system the feedback signal may be filtered by a BPF whose fundamental frequency is set to the selected frequency, to thus obtain an interference free feedback signal and, consequently, a reliable control of the electrosurgical system.

FIELD OF THE INVENTION

The present disclosure relates to electrosurgical systems. Moreparticularly, the present disclosure is directed to methods for reducingradio frequency (“RF”) interferences between electrosurgical systemsduring electrosurgical procedures, and to an electrosurgical system thatuses the methods.

BACKGROUND

Surgery is sometimes performed using an energy delivering system.Various types of therapeutic energies (e.g., electrical, RF, ultrasonic,microwave, cryogenic, heat, laser, etc.) may be used to treat a tissue.Electrosurgery is a tissue treating technique involving delivery of highRF electrical energy (e.g., 1-70 watts in bipolar and autobipolarelectrosurgical systems, 1-300 watts in monopolar electrosurgicalsystems). Electrosurgical treatment is rendered by an electrosurgicalsystem via an electrosurgical device (e.g., electrosurgical forceps, atreatment electrode and a dispersive neutral electrode (REM) pad).Electrosurgical RF generators differ widely in their output (energycarrier) RF, which may be approximately between 300 KHz and 480 KHz.There are three main types of electrosurgical systems: monopolarelectrosurgical systems, bipolar electrosurgical systems and autobipolarelectrosurgical systems.

Each electrosurgical system controls its operation state or mode(including transitioning between states and transitioning betweenoperation modes) by using a feedback signal that is produced fromelectrical current samples and/or voltage samples that reflect,represent or are derived from the system's output RF energy. Controllingthe state or operation mode of an electrosurgical system may includecontrolling an electrical parameter of the electrosurgical system, forexample an electrical current that the electrosurgical system outputs,an electrical voltage that the electrosurgical system outputs or anelectrical power of a therapeutic RF energy that the electrosurgicalsystem outputs. Regardless of the type of the electrosurgical systemthat is used, using a reliable feedback signal is prerequisite to properoperation of the electrosurgical system, and thus to the RF treatmentefficacy.

In some instances, conventional electrosurgical systems outputtherapeutic RF energy by using a same, or a similar, frequency. When two(or more) electrosurgical systems, which use a same, or a similar,carrier RF, treat two sites of a patient at a same time, it may occurthat a therapeutic energy, when applied to one site by a firstelectrosurgical system, would interfere with the feedback signal ofanother electrosurgical system, and thus with the operation of the otherelectrosurgical system. One example scenario where two treatment sitesare treated at the same time is a medical procedure known as coronaryartery bypass grafting (“CABG”) which involves cardiac vein harvestingfrom the leg and implanting the harvested cardiac vein in another sitewhere the vein is needed. In another scenario, a spine may be operatedat two surgical sites by using two electrosurgical systems at a sametime.

The interference an electrosurgical system may be subjected to is due toa remote therapeutic (high power) RF energy of another electrosurgicalsystem that is superimposed on the feedback signal that is used tocontrol the operation of the interfered with electrosurgical system. Thefeedback signal and an interfering therapeutic RF energy may jointly besubjected to constructive interference or to destructive interference,which makes the feedback signal susceptible to RF interferences thatoriginate, for example, from other electrosurgical systems and have anidentical, or similar, RF frequency. If the frequency of the feedbacksignal in one electrosurgical system and the frequency of thetherapeutic RF energy are close (rather than being identical),alternating constructive interference and destructive interference mayproduce “beats” in the feedback signal, which would impair (distort,deform) the feedback signal, making it unreliable.

It would, therefore, be beneficial to have methods and system thatenable simultaneous and independent operation of multipleelectrosurgical systems without the electrosurgical systems interferingwith one another during an electrosurgical procedure.

SUMMARY

Methods and system are provided, which mitigate RF interferences duringoperation of an electrosurgical system. A method, in some embodiments,may include refraining from outputting RF energy and, using a band passfilter (“BPF”), measuring an RF interference for a group of candidatefrequencies, selecting a frequency from the group of candidatefrequencies for which the measured RF interference is below a thresholdvalue, or the lowest, generating (and optionally outputting) RF energyat the selected frequency, and controlling operation of theelectrosurgical system by using a feedback signal that is derived from,or represents, or sampled from the generated or output RF energy and hasthe selected frequency. Depending on the type of the electrosurgicalsystem and on the system's operation mode, the RF energy that theelectrosurgical system outputs may be therapeutic energy orinterrogation signal, and the feedback signal may be filtered by a BPFwhose center (fundamental) frequency is set to the selected frequency.

Controlling the operation of the electrosurgical system may include, forexample, calculating from, or by using, the feedback signal, a value ofan operational parameter of the electrosurgical system, and controllingthe operation of the electrosurgical system based on the calculatedvalue of the operational parameter. In some embodiments the operationalparameter used to control the operation of the electrosurgical systemmay be an impedance (Z) at the output of the electrosurgical system, andcontrolling the operation of the electrosurgical system may includecontrolling an output electric current (I) of the electrosurgicalsystem, or an output electric voltage (V) of the electrosurgical systemsite, or an electrical power (P) of the RF energy that is output by theelectrosurgical system, or any combination thereof.

The electrosurgical system subject of the present invention may be amonopolar electrosurgical system, a bipolar electrosurgical system anautobipolar electrosurgical system, and the like. Each electrosurgicalsystem (regardless of its type) may produce the feedback signal at theselected frequency, and the feedback signal may be derived from thetherapeutic RF energy that the electrosurgical system outputs when itoperates in the treatment mode. In some cases (for example when theelectrosurgical system is an autobipolar electrosurgical system), thefeedback signal may be derived from an interrogation signal, or energy,that is generated by the electrosurgical system in an interrogation modeof operation before the electrosurgical system transitions to thetreatment mode. The electrosurgical system may transition from theinterrogation mode to the treatment mode, and vice versa, based, forexample, on the impedance (Z) at the output of the electrosurgicalsystem and/or based on another electrical parameter.

Measuring an RF interference for each particular frequency in the groupof candidate frequencies may include, for example, configuring a BPF topass only signals having the particular frequency. The band pass filtermay be implemented as a Goertzel filter, and the frequencies included inthe frequency group may be selected such that they satisfy a coherentsampling condition in order for them to coincide with null points in afrequency response (magnitude-frequency curve) of the filter.

In some embodiments a method of mitigating RF interferences duringoperation of an electrosurgical system may include performing, by anelectrosurgical system that is configured to output an RF energy,refraining from outputting RF energy and, while refraining fromoutputting RF energy, measuring an RF interference for each candidatefrequency in a group of candidate frequencies, selecting a frequencyfrom the group of candidate frequencies for which the measured RFinterference is below a predetermined threshold, or the lowest andoutputting RF energy at the selected frequency, calculating an impedance(Z) at the output of the electrosurgical system by using a feedbacksignal that is derived from the RF energy and has the selectedfrequency, and controlling operation of the electrosurgical system byusing the calculated impedance (Z).

Controlling the operation of the electrosurgical system may includecontrolling, during treatment delivery, an output electrical current ofthe electrosurgical system or an output electrical voltage of theelectrosurgical system or an electrical power of the RF energy, or anycombination thereof. Controlling the operation of the electrosurgicalsystem may also include determining a state or an operational mode ofthe electrosurgical system, for example determining, during therapeuticRF energy delivery, whether or when to transition the electrosurgicalsystem from the treatment mode in which the electrosurgical systemoutputs (high power) therapeutic RF energy, to the interrogation mode inwhich the electrosurgical system outputs a low power interrogationsignal (e.g., to measure impedance at the system's output in order todetermine whether or when to transition the electrosurgical system tothe treatment mode), and, while operating in the interrogation mode,whether or when to transition the electrosurgical system back to thetreatment mode. Controlling the operation of the electrosurgical systemmay also include controlling an output electric current of theelectrosurgical system, an output electric voltage of theelectrosurgical system, an output electrical power of the RF energy thatthe electrosurgical system outputs, and/or determining a state and/or anoperation mode of the electrosurgical system.

The electrosurgical system may include an electrosurgical generator togenerate therapeutic RF energy, a controller to control the operation ofthe electrosurgical generator, and a data storage that stores a group ofcandidate frequencies and parameters and/or coefficients that define, orthat enable to configure, a configurable BPF. The controller may beconfigured to: (i) cause the electrosurgical generator to refrain fromoutputting RF energy and, while doing that, to measure an RFinterference for each frequency in the group of candidate frequencies,(ii) select a frequency from the group of candidate frequencies forwhich the measured RF interference is below a predetermined threshold,or the lowest, and cause the electrosurgical generator to generate (and,optionally, to output) RF energy at the selected frequency, and (iii)control operation of the electrosurgical system by using a feedbacksignal that is derived (e.g., sampled) from the generated/output RFenergy. (Being derived; e.g., by sampling samples from a generated RFenergy, the feedback signal also has the selected frequency.)

The controller may be configured to calculate an impedance (Z) at theoutput of the electrosurgical system from the feedback signal (e.g.,from voltage and current samples), and to control, based on thecalculated impedance, an output electric current (I) of theelectrosurgical system, or an output electric voltage (V) of theelectrosurgical system site, or an electrical power (P) of the RF energythat is output by the electrosurgical system. The controller may usevoltage samples or current samples that may be taken from the output RFenergy, or both voltage and current samples, to control any electricalparameter (e.g., output current, output voltage, output power) of the RFenergy that the related electrosurgical system outputs, and/or tocontrol the state or operation mode of the related electrosurgicalsystem.

BRIEF DESCRIPTION OF THE DRAWINGS

Various exemplary embodiments are illustrated in the accompanyingfigures with the intent that these examples not be restrictive. It willbe appreciated that for simplicity and clarity of the illustration,elements shown in the figures referenced below are not necessarily drawnto scale. Also, where considered appropriate, reference numerals may berepeated among the figures to indicate like, corresponding or analogouselements. Of the accompanying figures:

FIGS. 1A and 1B schematically illustrate electrosurgical systems indifferent electrosurgical treatment setups where operation of oneelectrosurgical system may interfere with the operation of anotherelectrosurgical system;

FIG. 2A shows a plot illustrating ideal situation in the context ofimpedance evaluation in autobipolar systems;

FIG. 2B shows a plot illustrating interference-free realistic situationsin the context of autobipolar systems;

FIG. 2C shows an effect of RF interference on the plot of FIG. 2B;

FIG. 3 shows an effect of an RF interference on a feedback signal thatan electrosurgical system uses to control its state and/or outputelectrical parameter;

FIG. 4 shows a block diagram of an electrosurgical system according toan example embodiment;

FIG. 5 shows a method for mitigating RF interferences in anelectrosurgical system according to an example embodiment;

FIG. 6 shows a method for mitigating RF interferences in anelectrosurgical system according to another example embodiment;

FIG. 7 shows a method for mitigating RF interferences in anelectrosurgical system according to yet another example embodiment; and

FIG. 8 shows an example application of a magnitude-frequency response ofa BPF in accordance with an example embodiment.

DETAILED DESCRIPTION

The description that follows provides various details of exemplaryembodiments. However, this description is not intended to limit thescope of the claims but instead to explain various principles of theinvention and the manner of practicing it.

Although embodiments of the invention are not limited in this regard,discussions utilizing terms such as, for example, “processing,”“computing,” “calculating,” “determining”, “estimating”, “evaluating”,“analyzing”, “checking”, or the like, may refer to operation(s) and/orprocess(es) of a computer, a computing system or other electroniccomputing device (e.g., controller), that manipulate and/or transformdata represented as physical (e.g., electronic) quantities within thecomputer's registers and/or memories into other data similarlyrepresented as physical quantities within the computer's registersand/or memories or other information non-transitory storage medium thatmay store instructions to perform operations and/or processes. Unlessexplicitly stated, the method embodiments described herein are notlimited to a particular order or sequence. Additionally, some of thedescribed method embodiments or steps thereof can, for example, occur orbe performed at the same point in time.

The present disclosure discloses methods and system for ensuring that afeedback signal, which an electrosurgical system uses for controlling,for example, an operational parameter of the electrosurgical systemand/or its operational state or mode of operation, is not affected, oronly negligibly affected, by RF interferences originating from a nearbyelectrosurgical system. Briefly, a group of strictly selected RFfrequencies (which are referred to herein as “candidate frequencies”)are selected for an electrosurgical system as potential RF carrierfrequencies which the electrosurgical system may use to output RFenergy, and a suitable candidate frequency (a ‘quiet’, or the quietest,frequency in terms of RF interferences) may be selected from thefrequency group, thus ensuring an interference-free control of theelectrosurgical system throughout its operation range and states. If acandidate frequency selected for an electrosurgical system gets noisy(if it is interfered with), a different, quieter (less interfered with),carrier frequency may be selected (from the group of candidatefrequencies) for use by the electrosurgical system.

The term “feedback signal”, as used herein, may represent any type ofsignal, data or information that an electrosurgical system may producefrom voltage samples and/or from electrical current samples, or fromboth current and voltage samples of an RF energy that theelectrosurgical generator of the electrosurgical system generates duringoperation in order to control an electrical parameter (e.g., electricalcurrent, electrical voltage and electrical power at the electrosurgicalsystem's output) and/or a state and/or an operation mode of theelectrosurgical system. The type of feedback signal that anelectrosurgical system use may change during the operation of theelectrosurgical system, for example depending on the electrical current,voltage or power (or any combination thereof) at the output of theelectrosurgical system, and/or depending on a current state or operationmode of the electrosurgical system.

FIGS. 1A and 1B schematically illustrate electrosurgical systems indifferent electrosurgical treatment setups where operation of oneelectrosurgical system may interfere with the operation of anotherelectrosurgical system. Referring to FIG. 1A, a first electrosurgicalgenerator 110 and a second electrosurgical generator 120 operate on twoseparate treatment sites 130 and 140 of a human (or another mammal's)body 150. Treatment sites 130 and 140 may be relatively close (e.g.,they may be spaced 10 centimeters away from one another) or far apartfrom each other (e.g., 1.5 meter away from each other).

Both electrosurgical generator 110 and electrosurgical generator 120 aremonopolar electrosurgical systems. Electrosurgical generator 110includes a treatment electrode 160 via which electrosurgical generator110 may deliver RF therapeutic signal (V1(f 1)) to treatment site 130,and a REM pad 162. Similarly, electrosurgical generator 120 includes atreatment electrode 170 via which electrosurgical generator 120 maydeliver RF therapeutic signal (V2(f 1)) to treatment site 140, and a REMpad 172.

Electrosurgical generator 110 and electrosurgical generator 120 use acontinuous feedback signal to continually control their operation, forexample to control their output electrical current, or their outputelectrical voltage, or the power of their output RF therapeutic energy.The value of the feedback signal that is used to control the relatedelectrosurgical system may be relatively small, which may make thefeedback signal susceptible (‘sensitive’) to interferences in the samefrequency band.

In some instances (depending; e.g., on the modalities used), the valueof the feedback signals in electrosurgical system 110 and 120 may notnecessarily be relatively small. However, interference may become anissue when the feedback signal used by, for example, generator 110 isrelatively small in relation to the feedback signal that is used by, forexample, generator 120, or vice versa. This would occur, for example, ifone electrosurgical generator is attempting to deliver a low RFtherapeutic power to a body site while the other electrosurgicalgenerator is attempting to deliver a high RF therapeutic power to adifferent (e.g., nearby) body site.

By way of example, both electrosurgical generators 110 and 120 outputtherapeutic energy at the same carrier frequency, f1. Therefore, whenone electrosurgical generator (for example electrosurgical generator110) outputs a therapeutic RF signal at frequency f1, the feedbacksignal (which is produced using current samples, or voltage samples, orboth types of samples, of the RF signal, and, therefore, also has thesame frequency, f1) that electrosurgical generator 120 (to continue theexample) uses to control its own operation is interfered with by thetherapeutic RF energy that is output by electrosurgical generator 110.(The RF interference, which is a portion of the RF energy that electrode160 ‘transmits’ to electrode 170 (due to the electrodes undesirablyserving as an RF antenna), is conceptually shown at 180.) RFinterference between electrosurgical generator 110 and electrosurgicalgenerator 120 may be mutual; that is, treatment electrode 160 ofelectrosurgical generator 110 may receive a similar RF interference fromtreatment electrode 170 when electrosurgical generator 120 outputstherapeutic RF signal via electrode 170. In other words, due toinductive coupling between the electrodes (and the related wires), theyact as RF antennae that transmit and receive RF interference signalsthrough air and/or through the body of the subject undergoing theelectrosurgical procedure. Another type of interference signal that maydetrimentally affect a system's feedback signal may result from strayelectrical signals 182 that may travel between the electrodes throughthe body of the subject undergoing the electrosurgicalprocedure/treatment.

FIG. 1B shows a two-generator system where electrosurgical generator 110(a monopolar electrosurgical system) of FIG. 1A is replaced with abipolar electrosurgical generator 112. Like monopolar electrosurgicalgenerator 110, bipolar electrosurgical generator 112 also outputstherapeutic RF signal (V3(f 1)) via bipolar electrodes 190. Some of theRF energy that bipolar electrosurgical generator 112 outputs astherapeutic RF energy may interfere with the feedback signal, andtherefore the operation, of monopolar electrosurgical generator 120.(The RF interference that bipolar electrosurgical generator 112 imposeson electrosurgical generator 120 is conceptually shown at 184.)

RF interference between bipolar electrosurgical generator 112 andelectrosurgical generator 120 may be mutual: the RF interference causedby bipolar electrosurgical generator 112 during treatment interfereswith the feedback signal that monopolar electrosurgical generator 120uses for its operation, and the RF interference caused by monopolarelectrosurgical generator 120 during treatment interferes with thefeedback signal that bipolar electrosurgical generator 112 uses tocontrol its operation.

FIG. 2A shows a plot 200 illustrating an ideal situation in the contextof an autobipolar (“ABP”) electrosurgical system. The horizontal axisindicates a state/condition of the ABP electrosurgical system; e.g.,system's output circuit is closed versus open. The vertical axisconceptually indicates an external output impedance (Z) at the output ofthe electrosurgical system or at the tip of the electrosurgical device(e.g., at the tip of treatment forceps), though the impedance at thesetwo locations may differ. (The same applies to the axes in FIG. 2B,which is described below.) As described herein, impedance at the outputof the electrosurgical system is calculated (estimated) by samplingcurrent and voltage at the output of the electrosurgical system, and ifthe current and voltage samples are impaired by RF interferences,estimation of the impedance may likely to be unreliable.

When an electrosurgical system performs an electrosurgical procedure,the electrosurgical device (e.g., forceps) delivering treatment may, attimes, touch the treated bodily organ or tissue, and at other times itmay be intentionally moved away from the treatment site, for example, inorder not to provide excess energy to the treated tissue/site, forexample in order not to overheat, or otherwise damage, the treatedtissue/site. (The treatment delivering device may, at times, beunintentionally moved away from the treatment site.)

In ideal cases, when the treatment device touches the treated tissue(e.g., when the ABP system's electrical circuitry (the electrosurgicalsystem's ‘output circuitry’, or ‘output circuitry’ for short) is closedvia the tissue), the ABP system would sense a relatively small impedance(Z1, FIG. 2A), which is approximately the impedance of the tissue, andwhen the treatment device does not touch the treated tissue (i.e., whenthe ABP system's output circuitry is open), the impedance that the ABPsystem would sense should theoretically be infinite (Z_(∞), FIG. 2A),or, in practice, at least in the order of tens of kilo ohms.

As shown in FIG. 2A, the impedance gap ΔZ1 (FIG. 2A) between Z1 (theimpedance in the ‘closed circuit’ state) and Z_(∞), (the impedance inthe ‘open circuit’ state) is very large so that the two distinctimpedance states (Z1 and Z_(∞)) can be distinguished easily. Since theABP system should stop delivering therapeutic RF energy when thetreatment device is moved away from the body, the ability to reliablydistinguish between the two impedance states (Z1 and Z_(∞)) isprerequisite to safe, reliable and efficient operation of theelectrosurgical system. However, in practice, the impedance gap is farfrom being ideal, in part due to the parasitic capacitances existing inthe output circuitry of the electrosurgical system (and also in theelectrosurgical system itself), as demonstrated in FIG. 2B, which isdescribed below.

FIG. 2B shows a plot 210 illustrating example interference-freesituations in the context of an ABP system. When the treatment device(e.g., forceps) touches a treated tissue, see device condition 220;i.e., when the ABP system's output circuitry is closed via the tissue,the ABP system typically senses a relatively small impedance (under line250) that may change, for example, according to changes in thephysiological properties of the tissue, for example, while the tissue istreated. As shown in FIG. 2B, the impedance in the closed circuit state(220) may vary within ΔZ2, which can be within the range of tenths ofohms to kilo ohms, for example.

When the treatment device stops touching the treated site, causing theABP system's output circuitry to open (system condition 230), the outputimpedance that the ABP system typically senses in ‘open circuit’ state230 is higher than the impedance usually sensed by the ABP system in the‘closed circuit’ state (120), but still, it is much lower than desiredbecause of the parasitic impedance imposed on the system's outputcircuitry by the periphery equipment setting.

As shown in FIG. 2B, the impedance variations in the ‘open circuit’state (230) can have a magnitude that may be as large as ΔZ3, which canbe within the range of hundreds of ohms to tens of kilo ohms. The‘in-between state’ impedance gap ΔZ4 between the minimum ‘open circuit’impedance (240) and the maximum ‘closed circuit’ impedance (250) may be,in some systems, 4 kilo ohms, which is much smaller than the idealimpedance gap ΔZ1 (FIG. 2A) (Z1<<ΔZ1; ΔZ1→∞). (Line 250 may represent avalue of 2.2 kilo ohms, which is a practical value in some systems.)Because the impedance gap ΔZ4, which is a result of a feedback signalhaving a certain RF carrier frequency, is relatively narrow, it issusceptible to RF interferences that have the same, or similar, RFfrequency. Under certain conditions, using a same, or similar frequencymay result in a wrong decision with respect to the state (‘open circuit’or ‘closed circuit’) of the electrosurgical system, as schematicallyillustrated in FIG. 2C, which is described below.

FIG. 2C shows two plots 260 and 270 that illustrate an impact of an RFinterference on a feedback signal in the context of an ABP system thatoperates in the interrogation mode. Plot 260 shows a systemcondition/state as a function of time. For example, during time periodsT1, T3 and T5 the electrosurgical system does not output RF therapeuticenergy, and during time periods T2 and T4 the electrosurgical systemoutputs RF therapeutic energy, at 262 and at 264. Plot 270 illustratesthe effect of the therapeutic RF energy (at 262 and at 264) on anautobipolar electrosurgical system that operates at the same time onanother treatment site of a same subject.

When the autobipolar electrosurgical system is at the closed circuitstate (at 222), the RF interference shown at 262, being (in thisexample) a constructive interference, may cause the impedance, which iscomputed by the autobipolar electrosurgical system by using interferedwith voltage and current samples, to be greater than it actually is.(The difference in the value of the impedance caused by the interferenceis shown as ΔZ5.) As a result of this impedance miscalculation, thevalue of the impedance may be greater than the minimum value (go aboveline 240) above which the autobipolar electrosurgical system may stoptreatment and, optionally (e.g., depending on the type ofelectrosurgical system), transition to the interrogation mode. (As aresult of this, the autobipolar electrosurgical system may transitionfrom the interrogation mode to the treatment mode even though theelectrosurgical forceps do not touch the body of the subject.)

When the autobipolar electrosurgical system is at the open circuit state(at 232), the RF interference shown at 264, being (in this example) adestructive interference, may cause the impedance, which is measured bythe autobipolar electrosurgical system, to be lower than it actually is.(The difference in the value of the impedance caused by the interferenceis shown as ΔZ6.) As a result of this impedance miscalculation, thevalue of the impedance may be lower than the maximum value (line 250)below which the autobipolar electrosurgical system may transition fromthe interrogation mode to the treatment mode. (As a result of this, theautobipolar electrosurgical system may transition from the treatmentmode to the interrogation mode even though the electrosurgical forcepstouch the body of the subject.)

When the autobipolar electrosurgical system is in the treatment mode, itcontinues to sample voltage and current at the output of theelectrosurgical system, and to produce, from either voltage samples orcurrent samples or from both types of samples, a feedback signal tocontrol the system's output current, voltage or power, or system's stateor operation mode. Depending on the state or operation mode of theelectrosurgical system, it may use voltage and current samples tocompute (evaluate) the output impedance of the electrosurgical system,and use the computed impedance (solely or in combination with currentsamples and/or voltage samples) to control the state of theelectrosurgical system and/or the system's output current, voltage orpower

FIG. 3 shows two plots 300 and 302 that illustrate an effect of an RFinterference on a feedback signal in a general case. (These plots may beapplicable to all types of electrosurgical systems.) Plot 300 shows asystem condition/state of a first electrosurgical system (designated as“System-1” in FIG. 3) as a function of time. For example, during timeperiods T1, T3 and T5 System-1 does not output RF therapeutic energy,and during time periods T2 and T4 System-1 outputs RF therapeuticenergy, at 310 and at 320, at some carrier frequency. Plot 302illustrates the effect of the RF therapeutic energy (at 310 and at 320)on the feedback signal of a second electrosurgical system (designated as“System-2” in FIG. 3) that operates at the same time on another site ofa same subject, and using the same, or similar, carrier frequency asSystem-1. (Each of System-1 and System-2 can be any type ofelectrosurgical system.)

Assume that during time period 330 System-2 is in the treatment mode ofoperation. During time period 330, System-2 may use a continuousfeedback signal 340 to continually control the system's outputelectrical current, voltage or output power, and, if the system is anautobipolar electrosurgical system, also to determine whether the systemis to transition from the treatment mode to the interrogation mode. Thefeedback signal may be derived (e.g., computed) from current samplesand/or voltage samples that are continuously read to reflect theelectrical condition or state of the electrosurgical system at any time.

Being (in this example) a constructive interference, RF interference 310may increase the value of feedback signal 340, as shown at 350. Being(in this example) a destructive interference, RF interference 320decreases the value of feedback signal 340, as shown at 360. The extentof the increase (Δ1 in FIG. 3) and the decrease (Δ2 in FIG. 3) in thevalue of feedback signal 340 depend, among other things, on theintensity of the RF interference. Since the electrosurgical systemaffected by the RF interference makes operational decisions based on thevalue of the feedback signal, which may be produced from interfered withcurrent samples and/or interfered with voltage samples, it may take awrong decision due to its incorrect value. For example, System-2 (theelectrosurgical system experiencing RF interference in FIG. 3) maydetermine to control its output electrical current instead ofcontrolling its output voltage, or (in another example) to control itsoutput therapeutic RF energy instead of controlling its output voltage,or (in another example) System-2 may inefficiently control an electricalparameter (e.g., its output electrical current, voltage or power), etc.

FIG. 4 is a block diagram of an electrosurgical system 410.Electrosurgical unit 410 may include an electrosurgical generator 430(e.g., an RF signal/energy generator), a voltage monitoring circuit(“VMC”) 440, a current monitoring circuit (“CMC”) 450, a data storage470 and a controller 480 to control operation of electrosurgicalgenerator 430. Electrosurgical system 410 may also include a connectoror adapter 414 via which electrosurgical generator 430 outputstherapeutic RF energy and, depending on the type of electrosurgicalsystem, also interrogation signal/energy. In general, controller 480 maycontrol an electrical parameter of electrosurgical system 410 (e.g.,output current, voltage or power), and it may also control the state ofoperation mode of electrosurgical system 410.

If electrosurgical system 410 is an autobipolar system, electrosurgicalgenerator 430 may, at times, generate low energy RF interrogationsignal, for example less than 1 watt, for example at a ‘carrier’frequency within the range 300 KHZ-500 KHz, for example, during animpedance monitoring/interrogation phase (by using an interrogation modeof the system). Electrosurgical generator 430 may also generate highenergy (e.g., 1-70 watt) therapeutic RF signal that electrosurgicalsystem 410 may deliver, during an electrosurgical procedure (in atreatment mode of operation), to a bodily organ or tissue site (e.g.,electrosurgical site 404) of a subject 406.

An electrosurgical generator may use a same frequency for bothoutputting therapeutic RF energy and for generating a feedback signal,or it may use separate frequencies for these functions, as describedbelow in more detail:

-   1. A monopolar electrosurgical generator may be interfered with by    another electrosurgical generator if it uses the same (or a too    close) frequency as the interfering electrosurgical generator. In    this scenario, the RF frequency of the feedback signal and the RF    frequency of the output RF signal of the interfered with generator    are the same, because the feedback signal is sampled ‘out’ (e.g.,    derived from) from the system's output RF signal.-   2. In an autobipolar electrosurgical generator, however, impedance    interrogation signal is not sampled/derived from therapeutic RF    energy, but, rather, is generated between therapeutic RF energy    activations (‘bursts’). Therefore, the frequency of the impedance    interrogation signal and the frequency of generator's output RF    signal can differ. In such a case, the autobipolar generator might    be interfered with if the interfering generator outputs an RF energy    whose frequency is identical, or too close, to the frequency of the    impedance interrogation signal. (The interfered with generator may    use a different frequency to output RF therapeutic energy.)

Electrosurgical system 410 may deliver the therapeutic RF energy thatelectrosurgical generator 430 generates to site 404 via anelectrosurgical device, which, in the case of a monopolar system,includes one electrode 418 and a REM pad 422. In the case that theelectrosurgical device is a bipolar system, the electrosurgical devicemay include a pair of two electrode tines. (The electrosurgical deviceis a device delivering therapeutic RF energy from the electrosurgicalsystem to the treated site in order to perform various surgicaloperations, for example coagulation, ablation, cutting and/or otheroperations.)

Controller 480 may receive (e.g., from a user; e.g., from a surgeonoperating the system), for example by using a hand switch or a footswitch, an input signal or a message 482 instructing controller 480 totransition electrosurgical system 410 to the treatment mode in whichelectrosurgical generator 430 generates therapeutic (high power) RFenergy, or to stop generating therapeutic RF energy. Alternatively, thisfunction may be performed automatically by controller 480, which maycontrol operation of a monopolar electrosurgical system or a bipolarelectrosurgical system. For example, controller 480 may determine whenan operation mode of the electrosurgical system should be activated(transitioned to), deactivated, resumed, etc. based on a feedbacksignal, which reflects, represents, is related to or derived (e.g.,sampled) from the output RF energy, that controller 480 may receive, forexample, from VMC 440, or from CMC 450, or from both current and voltagemonitoring/sampling circuits 440 and 450. (In case a control schemerelies on the electrosurgical system's output impedance, the feedbacksignal may include, or may take into account or factor in, bothelectrical current samples and electrical voltage samples.) The feedbacksignal may reflect, represent, be related to or be derived from voltageVin (shown at 424) that VMC 440 samples between points 432 and 434, orreflect, represent, be related to or derived from the system's outputcurrent 452 that CMC 450 samples, or correspond to or reflect,represent, be related to or derived from both voltage samples andcurrent samples which are respectively sampled by VMC 440 and CMC 450.

Controller 480 may receive, from VMC 440 and/or from CMC 450, signal(s),voltage samples and/or current samples, or data that represent thefeedback signal. Alternatively, control 480 may receive digitizedvoltage samples and/or digitized current samples from VMC 440 and/orfrom CMC 450, and use the digitized samples to produce a feedback signalin order to effect any of the control schemes described herein. Anothertype of information that an electrosurgical system may use may beobtained (e.g., computed) from the output of multiple BPFs (Goertzelfilters), to independently filter voltage samples and current samples atspecific frequencies, for example at the candidate frequencies offrequency group 472. Regardless of the electrical parameter (current,voltage or power) that controller 480 controls, controlling theelectrical parameter is improved (e.g., is made more accurate relativeto a conventional electrosurgical system) because controller 480,selects for electrosurgical generator 430, a frequency that, among thecandidate frequencies, is the least susceptible to (including minimal)RF interferences.

Controller 480 may, at times, temporarily activate an interferencesensing mode in which controller 480 may sense RF interferences in eachfrequency in the group of candidate frequencies, and select for theelectrosurgical generator 430 a currently quiet, or the quietest,frequency among the candidate frequencies. Controller 480 may transitionto the interference sensing mode according to an interference sensinginterval in order to select the quiet, or the quietest, frequency forthe electrosurgical generator. For example, controller 480 maytransition to the interference sensing mode (i.e., transition to theinterference sensing mode) once every n1 seconds (e.g., n1=20 seconds,n1 may have other values), or once every n2 minutes (e.g., n2=5 minutes,n2 may have other values). (Other interference sensing intervals may beselected.)

In case electrosurgical system 410 is an autobipolar electrosurgicalsystem controller 480 may calculate, during an impedance interrogationphase, the system's instantaneous output impedance, Zout, by applying aninterrogation voltage, Vin, 424, and measuring that voltage by VMC 440,and by concurrently measuring the resulting interrogation current Iin(452) by CMC 450. Controller 480 may compute the output impedance Zout(Zout=Vin/Iin) and, based on the value of Zout, determine the nextoperation mode or state of electrosurgical system 410. ‘Knowing’ theoutput voltage (Vout) and output current (Tout) at treatment electrode418, controller 480 may also determine (and control) the therapeutic RFenergy actually provided to the treated site when the electrosurgicalsystem operates in the treatment mode. Knowing the actual therapeutic RFenergy delivered to the treated site, controller 480 may control (490)the operation (e.g., an output electrical parameter) of electrosurgicalgenerator 430 to deliver an optimal amount of therapeutic energy to thetreated site at any given time during treatment. When electrosurgicalgenerator 430 is not delivering therapeutic RF energy, it may deliver(in an autobipolar electrosurgical system), at times, a relatively smallaverage interrogation current 452 (e.g., in the order of micro amps),for example which is in compliance with IEC safety regulations, tointerrogate (sense, evaluate) the magnitude of a tissue impedance.

VMC 440 may include an isolation transformer that acts as an inductivepickup device. The transformer primary side may be electricallyconnected between lead points 432 and 434 for inducing a voltage signalon the transformer's secondary windings in response to the RF energythat electrosurgical generator 430 outputs through these points. VMC 450(a current sensing circuit) senses, as feedback, an electrical currentreturning to electrosurgical system 410 as a result of the RF energythat electrosurgical generator 430 outputs. Being sampled, or derived,from RF energy that the electrosurgical system outputs, voltage signal424 and current signal 452 are alternating current (AC) signals that(when in the treatment mode) represent the therapeutic RF energy thatelectrosurgical generator 430 outputs to the electrosurgical device inorder to control an electrical parameter (e.g., current, voltage, power)of the therapeutic RF energy, or (in the case of an autobipolarelectrosurgical system operating in the interrogation mode), that may beused to evaluate the output impedance of the electrosurgical system inorder to determine, for example, whether the electrosurgical system isto transition from the interrogation mode to the treatment (therapeuticRF energy delivering) mode.

In a bipolar configuration, the electrosurgical device includes twoelectrodes (not shown), which are used at a surgical site of the patientwith one electrode providing the return path for the output ofelectrosurgical generator 430. In a monopolar configuration, theelectrosurgical device includes one electrode 418 while anotherelectrode (422) is connected to a surface near the patient and providesthe return path. Although monopolar and bipolar configurations are usedin electrosurgical systems, they are electrically equivalent and equallysuited for use with the control methods and control system of thepresent disclosure.

In data storage 470 may be stored first data that represent a group, orlist, of candidate frequencies (f1, f2, f3, . . . ), and second datathat represent parameters (e.g., center frequency, filter width) and/orcoefficients that define a configurable band pass filter (BPF) andenable (e.g., controller 480) to configure the BPF to selectively passany frequency in the frequency group, according to need.

The RF energy that the electrosurgical system outputs (for therapy orfor impedance interrogation) is sampled (e.g., by VMC 440 and CMC 450)at a sampling frequency. Knowing in advance the frequency that anelectrosurgical system is going to use to deliver therapeutic RF energywhich, if ignored, may interfere with the operation of theelectrosurgical system subject of the invention, and also knowing thesampling frequency that the electrosurgical system subject of theinvention is to use to sample its own RF energy, enable to selectcandidate frequencies among which one candidate frequency may beselected as an operational frequency for the electrosurgical system. Tothis effect, each candidate frequency in the group of candidatefrequencies may be selected (as potential electrosurgical system'scarrier frequency, or, in some embodiments, as potential frequencies fora feedback signal) if it satisfies a sampling condition known in thefield of digital filters as the coherent sampling condition, which isgiven below:

$\frac{f_{in}}{f_{s}} = \frac{M_{cycles}}{N_{samples}}$where fin is a frequency of the RF energy (hence of the feedbacksignal), fs is a sampling frequency at which the electrosurgicalsystem's output voltage and/or output current (from which the feedbacksignal is produced) is sampled (e.g., by VMC 440 and CMC 450,respectively), Mcycles is the number of signal periods/cycles in asampled set (in a sampling window), and Nsamples is the number ofsamples in the sampled set (in the sampling window).

In an aspect of the invention, controller 480 may be configured to,among other things, activate the interference sensing mode of operation,which may include refraining (e.g., causing the electrosurgicalgenerator to refrain) from outputting RF energy and, while it refrainsfrom outputting RF energy, and measuring an RF interference for eachfrequency in the group of candidate frequencies. To this effect,controller 480 may use information stored in data storage 470 (e.g., BPFconfiguration parameters and/or coefficients 474) to configure a BPF toselectively pass signals having only the candidate frequencies, to thusmeasure interference for each candidate frequency. Then, controller 480may select a particular frequency from the group of candidatefrequencies for which the measured RF interference is below apredetermined threshold, or the lowest, and output RF energy at theselected frequency. Controller 480 may control the operation of theelectrosurgical system by using a feedback signal which is derived fromthe output RF energy and, like the output RF energy, has the sameselected frequency. To this effect, controller 480 may configure the BPFto pass only the particular frequency that controller 480 selects forthe electrosurgical system, and to reject (cancel out) the interferingRF signal(s). In this case, the frequency of the feedback signal is thesame as the frequency of the system's output RF energy. However, if anelectrosurgical system uses different frequencies for the feedbacksignal and output RF energy, controller 480 may assign the quietfrequency (or the lowest interfered with frequency) to the feedbacksignal in order for the feedback signal to be reliable, and configurethe BPF to pass only the feedback signal, and to reject (cancel out) theinterfering RF signal(s).

In another aspect of the invention, controller 480 may be configured,among other things, to refrain from outputting RF energy and to measurean RF interference for each frequency in the group of frequencies.Controller 480 may be also configured to select, for a feedback signal(a signal used to control the operation of the electrosurgical system),a frequency from the group of candidate frequencies for which themeasured RF interference is below a predetermined threshold, or thelowest, and to control operation of the electrosurgical system by usingthe feedback signal whose frequency is the selected frequency. Byselecting an operational (carrier) frequency for, or a frequency for afeedback signal to be used by, the electrosurgical system in the waydescribed herein, the interference problem that is described herein ismitigated.

In some embodiments, controller 480 may use the Goertzel filter as a BPFto process the voltage samples and the current samples. Measuringinterferences in the frequencies of the frequency group can be done byusing any kind of BPF, and measuring the feedback signal maybeneficially be done by using the Goertzel filter as a BPF.

In general, the BPF (e.g., a Goertzel filer) may be used in two phasesor ways:

(1) Sensing interferences—To sense RF interference in each RF frequencyin the group of candidate frequencies in order to identify a quiet, orthe quietest, RF frequency, and, after the quiet, or quietest, RFfrequency is identified, to use this frequency as the electrosurgicalsystem's feedback (control) signal and/or as the electrosurgicalsystem's RF carrier frequency (for outputting therapeutic RF energyand/or interrogation (RF) signals.(2) Control—After controller 480 selects the quietest RF frequency fromthe frequency group, and while using the selected frequency, controller480 may use the BPF to accurately (with interferences essentiallyeliminated or significantly diminished) measure a feedback signal thatoriginates (e.g., derived, or otherwise obtained) from, or represents

-   -   (2.1) Therapeutic RF energy that is output by an electrosurgical        system in order to control an electrical parameter of the        therapeutic RF energy that the electrosurgical system outputs.        In some cases an electrosurgical system may use a feedback        signal that originates from the therapeutic RF energy (in the        treatment mode) to determine whether the electrosurgical system        is to transition from one state to another, or from the        treatment mode to an interrogation mode.    -   (2.2) Non-therapeutic energy that is output by an        electrosurgical system, for example in the interrogation mode,        in order to, for example, evaluate the system's output impedance        in order to determine whether, or when, the electrosurgical        system is to transition, for example, from the interrogation        mode to the treatment mode.

In some embodiments, an electrosurgical system similar toelectrosurgical system 410 may include an electrosurgical generatorsimilar to electrosurgical generator 430, and a controller similar tocontroller 480, and the controller may be configured to cause theelectrosurgical generator to refrain from outputting RF energy, tomeasure an RF interference for each frequency in a group of candidatefrequencies when the electrosurgical generator refrains from outputtingRF energy, to select a frequency from the group of candidate frequenciesfor which the measured RF interference is below a predeterminedthreshold, or the lowest, and to control operation of theelectrosurgical system by using a feedback signal having a frequencywhich is set to the selected frequency. The feedback signal may bederived from an RF energy that is output by the electrosurgicalgenerator. For example, the RF energy may be therapeutic RF energy thatthe electrosurgical system outputs when it operates at a treatment mode,or an interrogation signal that the electrosurgical system outputs inorder to determine, for example, transitions between interrogation modeand treatment mode.

Carrier frequencies for electrosurgical systems typically range from 300KHz to 500 KHz, but some of these frequencies may be outside thosebounds under certain circumstances. For a particular sample rate underthe assumption of coherent sampling, the number of samples per signalperiod determines the possible carrier frequencies. For example, for asampling frequency of 20 million samples per second, the possiblecarrier frequency is computed by dividing the sample rate (frequency) bythe number of samples per one signal period. For example, 40 samples persignal period equates to (result in) a carrier frequency of 500 KHz; 50samples per signal period equates to a carrier frequency of 400 KHz, and60 samples per signal period equates to a carrier frequency of 333.33KHz. Therefore, over 20 possible carrier (candidate) frequencies satisfythe coherent sampling condition for the 20 million samples/secondapplication between 300 KHz and 500 KHz.

FIG. 5 shows a method for mitigating RF interferences during operationof an electrosurgical system according to an example embodiment. FIG. 5is described in association with FIG. 4. At step 510, controller 480 maytransition electrosurgical system 410 to an interference sensing mode inwhich controller 480 may refrain from outputting RF energy and, whilerefraining from outputting RF energy, controller 480 may measure RFinterferences in any candidate frequency in a group of candidatefrequencies (472) that may be stored/listed, for example, in datastorage 470. Controller 480 may use REM pad 422 as an RF antenna tosense RF interferences in the candidate frequencies one candidatefrequency at a time (e.g., one after another), or controller 480 maysense RF interferences in all the candidate frequencies at the sametime. Controller 480 may alternatively measure RF interferences using adedicated RF antenna. (A dedicated antenna, or sensor, may be mounted,or be part of, for example, REM pad 422.) Controller 480 may store (forexample in data storage 470) a value indicating or representing anintensity of a measured RF interference for each candidate frequency,for example, for comparison purpose.

At step 520, controller 480 may identify and select a candidatefrequency from the group of candidate frequencies for which the measuredRF interference is below a predetermined threshold, or the lowest, andcause electrosurgical generator 430 to generate RF energy at theselected candidate frequency. The type of RF energy that controller 480causes electrosurgical generator 430 to generate at the selectedcandidate frequency may depend on the state electrosurgical system 410is currently in, or on the operation mode actually used byelectrosurgical system 410, which may be of any type (e.g., bipolar,monopolar, autobipolar). (Electrode 418 and REM pad 422 are shown for amonopolar electrosurgical system. However, electrosurgical system 410may be bipolar (or autobipolar) electrosurgical system and theelectrodes delivering therapeutic RF energy may change accordingly.)

Regardless of the type of RF energy (therapeutic energy or interrogationenergy) that the electrosurgical generator 430 generates, VMC 440 andCMC 450 may respectively sample the electrosurgical system's outputvoltage and current and produce, from these samples, a feedback signalfor controller 480. Alternatively, VMC 440 and CMC 450 may transfer tocontroller 480 signals, voltage and current samples, or data, andcontroller 480 may use these samples, or some of them, to produce thefeedback signal required to control operation of the system, or part ofthe system. At step 530, controller 480 controls the operation ofelectrosurgical system 410 by using the feedback signal that was sampledfrom the generated RF energy.

Controller 480 may repeat (540) steps 510 through 530, for exampleaccording to a predetermined schedule (e.g., according to aninterference sensing interval), in order to ensure that the feedbacksignal produced from the voltage and/or current samples respectivelyobtained by VMC 440 and CMC 450 is reliable (i.e., not interfered with,for example, by an electrosurgical generator of another; e.g., nearby,electrosurgical system) throughout the entire, or at least during mostof the, electrosurgical procedure.

FIG. 5 refers to embodiments in which the frequency of the feedbacksignal and the frequency of the output therapeutic RF energy areidentical, and controller 480 assigns the quiet, or quietest, frequencyto the electrosurgical system to enable it to produce the two types ofsignals. FIG. 6, which is described below, refers to embodiments inwhich the frequency of the feedback signal and the frequency of theoutput RF energy are different, and controller 480 assigns the quiet, orquietest, frequency to the feedback signal (but not to the therapeuticRF energy) or, more specifically, to an electric circuit that outputs RFenergy from which the feedback signal is derived.

FIG. 6 shows a method for mitigating RF interferences during operationof an electrosurgical system according to another example embodiment.FIG. 6 is described in association with FIG. 4. At step 610, controller480 may transition electrosurgical system 410 to an interference sensingmode in which controller 480 may refrain from outputting RF energy, and,while refraining from outputting RF energy, measure RF interferences ineach candidate frequency in a group of candidate (RF) frequencies thatmay be stored (e.g., as a list, as a binary code, etc.), for example, indata storage 470. Controller 480 may sense RF interferences in eachparticular candidate frequency, for example, by setting a fundamentalfrequency of a BPF to the particular candidate frequency, and measuringthe filter's output at that RF frequency. At step 620, controller 480may identify and select a candidate (RF) frequency from the group ofcandidate (RF) frequencies for which the measured RF interference isbelow a predetermined threshold, or the lowest.

At step 630, controller 480 may operate electrosurgical system 410 usingthe selected RF frequency. Operating electrosurgical system 410 bycontroller 480 by using the selected RF frequency may include producinga feedback signal at the selected frequency, and controlling operationof the electrosurgical system by using the feedback signal. Controller480 may derive the feedback signal from a therapeutic RF energy that isoutput by the electrosurgical generator when the electrosurgical systemoperates at a treatment mode, or from an interrogation signal that isgenerated by the electrosurgical system before the electrosurgicalsystem transitions between an interrogation mode and the treatment mode.Controller 480 may use the feedback signal to calculate an impedance, Z,at the output of the electrosurgical system, and control the operationof the electrosurgical system by using the calculated impedance, Z. Atherapeutic RF energy and a feedback signal may have, in someembodiments, a same frequency, and, in other embodiments, they may havedifferent frequencies, with the feedback signal having the selected (RF)frequency.

Controlling the operation of electrosurgical system 410 by controller480 may include controlling an output electrical current and/or anoutput electrical voltage of electrosurgical system 410 and/or anelectrical power of the RF energy, and/or transitioning electrosurgicalsystem 410 between an interrogation mode of operation, in which itoutputs an interrogation signal, and a treatment mode, in which theelectrosurgical system may output therapeutic RF energy.

Controller 480 may repeat (640) steps 610 through 630, for exampleaccording to a predetermined schedule (e.g., according to aninterference sensing interval), in order to ensure that the feedbacksignal produced from the voltage and current samples respectivelyobtained by VMC 440 and CMC 450 is reliable (i.e., not interfered with,for example, by an electrosurgical generator of another; e.g., nearby,electrosurgical system) throughout the entire electrosurgical procedure.

FIG. 7 shows a method for mitigating RF interferences in, and duringoperation of, an electrosurgical system according to another exampleembodiment. FIG. 7 is described in association with FIG. 4. At step 710,controller 480 may transition electrosurgical system 410 to aninterference sensing mode in which controller 480 may refrain fromoutputting RF energy, and, while refraining from outputting RF energy,measure RF interferences in any candidate frequency in a group ofcandidate frequencies that may be listed 472, for example, in datastorage 470. Controller 480 may use electrode 418, or a dedicated RFantenna, to sense RF interferences in the candidate frequencies.Controller 480 may store (for example in data storage 470) a valueindicating an intensity of a measured RF interference for each candidatefrequency, for example, for comparison purpose.

At step 720, controller 480 may identify and select a candidatefrequency from the group of candidate frequencies for which the measuredRF interference is below a threshold value, or the lowest. Controller480 may, then, cause electrosurgical generator 430 to output RF energyat the selected frequency. As described herein, the RF energy thatcontroller 480 may cause electrosurgical generator 430 to output may behigh RF energy (for therapeutic use), or low RF energy (e.g., forimpedance interrogation use when the related electrosurgical system isin the interrogation mode). Controller 480 may use the system's outputimpedance to control a transitioning of the electrosurgical system fromone state or operation mode to another, or to control an electricalparameter of the RF energy that the electrosurgical system outputs, forexample during treatment. (As described herein, the system's outputimpedance is calculated from current and voltage samples that may beobtained (e.g., derived), for example, by VMC 440 and CMC 450, from thesystem's output RF energy.)

At step 730, controller 480 may compute the electrosurgical system'soutput impedance, Z, by using current and voltage samples of the outputRF energy, and, at step 740, controller 480 may control operation of theelectrosurgical system based on the compute impedance, Z. Controllingoperation of the electrosurgical system based on the compute impedance,Z, may be performed as described herein. For example, if the impedanceat the system's output is relatively low (e.g., lower than a thresholdimpedance value), controller 480 may control the system to a currentlimit, and if the impedance is relatively high (e.g., higher than athreshold impedance value), controller 480 may control the system to avoltage limit, and if the impedance is in a middle of the impedancerange (e.g., between these two impedance thresholds) for the activemodality, controller 480 may control the system's output power.

Controller 480 may repeat (750) steps 710 through 740, for exampleaccording to a predetermined schedule, in order to ensure that thefeedback signal derived from the voltage and current samples, which isthe basis for the control schemes described herein, is reliablethroughout the entire electrosurgical procedure.

In connection with the methods described herein, for example inconnection with FIGS. 5-7, controlling operation of the electrosurgicalsystem (for example by controller 480, FIG. 4) may include, for example,calculating by controller 480, from or using the feedback signal, avalue of an operational parameter of the electrosurgical system, andcontrolling, by controller 480, the operation of the electrosurgicalsystem based on the calculated value of the operational parameter. Thecalculated operational parameter may be, for example, an impedance (Z)measured at the output of the electrosurgical system, an RF energy powerthat the electrosurgical system outputs, etc. Controller 480 may controlthe operation of the electrosurgical system based on the calculatedimpedance, Z, for example by controlling an output electric current (I)of the electrosurgical system, or an output electric voltage (V) of theelectrosurgical system site, or an electrical power (P) of the RF energythat is output by the electrosurgical generator 430.

Controlling the operation of the electrosurgical system (e.g.,electrosurgical system 410) may include, for example, setting the BPF'sfundamental, or main, frequency to the selected frequency, and filteringthe feedback signal by the BPF whose fundamental, or main, frequency hasbeen set to the selected frequency.

FIG. 8 shows a frequency magnitude response graph 800 of a digital BPFaccording to an example embodiment. The frequency magnitude response ofthe BPF is equivalent to the sin(x)/x (sinc function) like magnituderesponse of a single bin of an N-point DFT, a portion of which is shownin FIG. 8. Using a BPF, if implemented as a Goertzel filter, enables todetect the presence of a single continuous-wave sinusoidal tone in asimple way, yet efficiently, and to effectively isolate a frequency ofinterest (‘tone’)—in our case individual candidate frequencies—for thepurpose of detecting RF interferences, and, during operation, to cancelout interferences whose frequency is different than the filter'smain/primary frequency. Therefore, using a Goertzel filter as the BPFfacilitates the selection of a quiet, or the quietest, carrier frequencyfor an electrosurgical generator, and, in particular, for the purpose ofobtaining an interference-free feedback signal which is prerequisite toaccurate and reliable control of any electrosurgical system.

Referring again to FIG. 8, assume that frequency magnitude responsecurve 810 is a frequency magnitude response curve of an interferingelectrosurgical system whose carrier frequency is f1 (e.g., f1=434,028KHz). The magnitude (in db) of frequency magnitude response curve 810spans between db(min) and db(max). Each point of frequency magnituderesponse curve 810 that has magnitude db(min) is a ‘null point’ of thefrequency magnitude response curve.

If two electrosurgical systems operate at a same carrier frequency f1,one electrosurgical system may interfere with the operation of the otherelectrosurgical system because of the constructive, or destructive,effect of the therapeutic RF energy of one electrosurgical system on thefeedback signal that the other electrosurgical system uses to controlits operation. If the carrier frequency of the interfered withelectrosurgical system is arbitrarily changed to, say, f11, or to f51,(that is, to a non-null point), the interference problem may still existbecause of the RF energy spill-over of the interfering RF energy (whichis generated using carrier frequency f1) to other frequencies. In otherwords, not every frequency that differs from the interfering frequency,f1, can solve the interference problem because energy of the interferingsignal, at frequency f1, spills-over to ‘neighboring’ frequencies,though this effect gradually decreases. However, every null frequency(‘null frequency’—a frequency that is located at, or coincides with, anull point in the frequency magnitude response graph) may solve theproblem because the energy spilled-over due to the interference islargely attenuated (e.g., to db(min), FIG. 8) at the nullpoints/frequencies. Therefore, if the interfered with electrosurgicalsystem selects a null frequency as its operational carrier frequency,the feedback signal used by the electrosurgical system to control itsoperation is, to a large degree, free of interference. If the feedbacksignal, which represents, or is derived from, the current and/or voltagesamples discussed herein, is interference free, the electrosurgicalsystem's parameter that is controlled (e.g., the electrosurgicalgenerator's output voltage and/or current and/or electrical power) canbe calculated accurately and reliably.

Referring again to FIG. 8, example null points of the filter are shownat ‘null’ frequencies f2, f3, f4 and f5. (The number of null frequenciesfrom which the interfered with electrosurgical system may select acandidate frequency as its carrier/operational frequency, or as afrequency of the feedback signal, may be less than four, or greater thanfour.) The second electrosurgical system may use any of the candidatenull frequencies f2, f3, f4 and f5 as its carrier frequency. However, itwould be beneficial for the interfered with electrosurgical system toidentify one of the null frequencies which is a quiet, or the quietest,frequency (e.g., a frequency which is the least interfered with by RFinterference).

By way of example, the interfering frequency, f1, may be equal to434,028 Hz, and the null (candidate) frequencies may have the followingvalues: f2=416,662 Hz, f3=425,120 Hz, f4=443,262 Hz, and f5=452,899 Hz.In general, the locations of the null points on the frequency axis ofthe frequency magnitude response graph are a result of the signal'ssampling frequency, and also a result of these frequencies satisfyingthe coherent sampling condition, so the signal's sampling frequency, andother factors, may conveniently be set or chosen such that the candidatefrequencies can be located at desired null locations on the frequencyaxis.

In some embodiments, when the candidate frequencies are known (e.g.,calculated in advance; e.g., based on coherent sampling, samplingfrequency, etc.) and stored in, for example, data storage 470 (FIG. 4),the controller (e.g., controller 480) controlling the electrosurgicalgenerator (e.g., electrosurgical generator 430) may initially operatethe electrosurgical generator using a default RF carrier frequency thatmay be included in the group of candidate frequencies. If an RFinterference is detected in the default RF carrier frequency, theelectrosurgical generator may ‘scan’ the list of available candidatefrequencies in the frequency group for the (maybe a different)“quietest” frequency, and replace the electrosurgical generator'sinterfered with RF carrier frequency with the quiet, or quieter, RFfrequency.

The articles “a” and “an” are used herein to refer to one or to morethan one (i.e., to at least one) of the grammatical object of thearticle, depending on the context. By way of example, depending on thecontext, “an element” can mean one element or more than one element. Theterm “including” is used herein to mean, and is used interchangeablywith, the phrase “including but not limited to”. The terms “or” and“and” are used herein to mean, and are used interchangeably with, theterm “and/or,” unless context clearly indicates otherwise. The term“such as” is used herein to mean, and is used interchangeably, with thephrase “such as but not limited to”.

Embodiments of the invention may include a computer or processornon-transitory storage medium, such as for example a memory, a diskdrive, or a USB flash memory, encoding, including or storinginstructions, e.g., computer-executable instructions, which whenexecuted by a processor or controller, carry out methods disclosedherein. Having thus described exemplary embodiments of the invention, itwill be apparent to those skilled in the art that modifications of thedisclosed embodiments will be within the scope of the invention.Alternative embodiments may, accordingly, include more modules, fewermodules and/or functionally equivalent modules. The present disclosureis relevant to various types of electrosurgical systems (e.g., bipolartype electrosurgical systems, autobipolar type electrosurgical systems,monopolar type electrosurgical systems, and the like) and to varioustypes of electrosurgical devices. Hence the scope of the claims thatfollow is not limited by the disclosure herein to any particularelectrosurgical system or electrosurgical device.

The invention claimed is:
 1. A method of mitigating interferences duringoperation of an electrosurgical system, comprising: by anelectrosurgical system configured to output a therapeutic radiofrequency (“RF”) energy, performing, refraining from outputting RFenergy; measuring, while refraining from outputting RF energy, an RFinterference for a group of candidate frequencies; selecting, from thegroup of candidate frequencies, a frequency for which the measured RFinterference is below a predetermined threshold and generating RF energyat the selected frequency; and controlling operation of theelectrosurgical system by using a feedback signal sampled from thegenerated RF energy.
 2. The method as in claim 1, wherein controllingthe operation of the electro surgical system comprises: calculating,using the feedback signal, a value of an operational parameter of theelectrosurgical system; and controlling the operation of theelectrosurgical system based on the calculated value of the operationalparameter.
 3. The method as in claim 2, wherein the calculatedoperational parameter is an impedance (Z) at the output of theelectrosurgical system.
 4. The method as in claim 2, wherein controllingthe operation of the electrosurgical system comprises controlling anoutput electric current (I) of the electrosurgical system, or an outputelectric voltage (V) of the electrosurgical system site, or anelectrical power (P) of the RF energy that is output by theelectrosurgical system, or determining a state or an operational mode ofthe electrosurgical system.
 5. The method as in claim 1, wherein theelectrosurgical system is selected from the group consisting of:monopolar electrosurgical system, bipolar electrosurgical system andautobipolar electrosurgical system, and wherein each of the monopolarelectrosurgical system, bipolar electrosurgical system and autobipolarelectrosurgical system is configured to produce the feedback signal atthe selected frequency.
 6. The method as in claim 5, wherein thefeedback signal is derived from therapeutic RF energy that theelectrosurgical system outputs.
 7. The method as in claim 5, wherein thefeedback signal is derived from an interrogation signal generated by theelectrosurgical system.
 8. The method as in claim 1, wherein measuringan RF interference for each particular frequency in the group ofcandidate frequencies comprises configuring a band pass filter to passonly the particular frequency.
 9. The method as in claim 8, wherein theband pass filter is a Goertzel filter.
 10. The method as in claim 8,wherein each candidate frequency satisfies the coherent samplingcondition: $\frac{f_{in}}{f_{s}} = \frac{M_{cycles}}{N_{samples}}$ wherefin is a frequency of the output RF energy, fs is a sampling frequency,Mcycles is the number of cycles in a sample set or in a sample window,and Nsamples is the number of samples in the sample set or in the samplewindow.
 11. The method as in claim 8, wherein controlling the operationof the electro surgical system comprises setting a frequency of the bandpass filter to the selected frequency and filtering the feedback signalby the band pass filter at the selected frequency.
 12. Anelectrosurgical system comprising: an electrosurgical generator tooutput therapeutic radio frequency (“RF”) energy; and a controller tocontrol operation of the electrosurgical generator; wherein thecontroller is configured to, cause said electrosurgical generator torefrain from outputting RF energy; measure an RF interference for eachfrequency in a group of candidate frequencies when the electrosurgicalgenerator refrains from outputting RF energy; select a frequency fromthe group of candidate frequencies for which the measured RFinterference is below a predetermined threshold; and control operationof the electrosurgical system, the control comprising using a feedbacksignal having the selected frequency.
 13. The electrosurgical system asin claim 12, wherein the controller is configured to derive the feedbacksignal from RF energy that the electrosurgical generator outputs. 14.The electrosurgical system as in claim 12, wherein each frequency in thegroup of candidate frequencies coincides with a null point of amagnitude-frequency response curve of a band pass filter.
 15. Theelectrosurgical system as in claim 14, wherein the band pass filter is aGoertzel filter.
 16. The electrosurgical system as in claim 12, whereineach candidate frequency satisfies the coherent sampling condition:$\frac{f_{in}}{f_{s}} = \frac{M_{cycles}}{N_{samples}}$ where fin is afrequency of the output RF energy, fs is a sampling frequency, Mcyclesis the number of cycles in a sample set or in a sample window, andNsamples is the number of samples in the sample set or in the samplewindow.
 17. The electrosurgical system as in claim 14, wherein thecontroller is configured to set the frequency of the band pass filter tothe selected frequency and to filter the feedback signal by the bandpass filter using the selected frequency.
 18. The electrosurgical systemas in claim 12, wherein the controller is configured to calculate animpedance (Z) at the output of the electrosurgical system from thefeedback signal, and to control, based on the calculated impedance, anoutput electric current (I) of the electrosurgical system, or an outputelectric voltage (V) of the electrosurgical system site, or anelectrical power (P) of the RF energy output by the electrosurgicalsystem, or a state of the electrosurgical system, or an operational modeof the electrosurgical system.
 19. A method of mitigating interferencesduring operation of an electrosurgical system, comprising: by anelectrosurgical system configured to output a therapeutic radiofrequency (RF) energy, performing, refraining from outputting RF energyand measuring an RF interference for a group of candidate frequencies;selecting a frequency from the group of candidate frequencies for whichthe measured RF interference is below a threshold value; producing afeedback signal at the selected frequency; and controlling operation ofthe electrosurgical system by using the feedback signal.
 20. The methodas in claim 19, wherein controlling the operation of the electrosurgical system comprises: controlling an output electrical current ofthe electrosurgical system or an output electrical voltage of theelectrosurgical system or an electrical power of the RF energy, ortransitioning the electrosurgical system between an interrogation modeof operation in which the electrosurgical system outputs an impedanceinterrogation signal, and a treatment mode of operation in which theelectrosurgical system outputs therapeutic RF energy, or controlling astate or an operational mode of the electrosurgical system.